High pressure lamp having a coil for magnetically stabilizing the discharge arc



313,980 FOR MAGNETICALLY E ARC pril 11, 1967 IL HA A. C. DUCATI HIGH PRESSURE LAMP HAVING A CO STABILIZING THE DISC a1 Filed Sept. 29, 1958 2 Sheets- 1 rigin BY M/k? Apr 11. 1967 A. c. DUCATl 3,31

HIGH PRESSURE LAMP HAVING A COIL FOR MAGNETICALLY STABILIZING THE DISCHARGE ARC Original Filed Sept. 29, 1958 2 Sheets-Sheet 2 /7C{ 22 /6a 25 /4a INVENTOR, .GZJQ/ANO CT ZX/Cflf/ United States Patent 3,313,980 HIGH PRESSURE LAMP HAVING A COIL FOR MAGNETICALLY STABILIZING THE DIS- CHARGE ARC Adriano C. Ducati, Santa Ana, Califi, assignor to Giannini Scientific Corporation, Amityville, N.Y., a corporation of Delaware Application May 23, 1962, Ser. No. 197,097, which is a continuation of abandoned application Ser. No. 763,926, Sept. 29, 1958. Divided and this application Nov. 12, 1964, Ser. No. 410,510

1 Claim. (Cl. 315-111) This application is a division of my copending patent application Ser. No. 197,097, filed May 23, 1962, for Electrical Discharge Apparatus and Method for Achieving High Temperatures and Mach Numbers and High- Intensity Light Pulses, now abandoned. Said application is a continuation of application Ser. No. 763,926, filed Sept. 29, 1958, for Electrical Discharge Apparatus and Method for Achieving High Temperatures and Mach Numbers, now abandoned.

This invention relates to an electrical discharge apparatus, and more particularly to an electrical discharge lamp.

The object of the invention is to provide an improved lamp apparatus wherein an electrical discharge is stabilized by means of magnetic fields.

This and other objects will become apparent from the following detailed description taken in connection with the accompanying drawings in which:

FIGURE 1 is a schematic view, partially in side eleva tion and partially in vertical central section, illustrating a first form of apparatus;

FIGURE 2 is an enlarged fragmentary central sectional view of the mid-portion of the showing of FIGURE 1;

FIGURE 3 is a fragmentary transverse section taken on line 33 of FIGURE 2;

FIGURE 4 is a view corresponding generally to FIG- URE 2 but illustrating a second form of apparatus, in which a discharge outlet is provided in only one of the electrodes;

FIGURE 5 is a view, partially in central section and partially in side elevation, illustrating a third form of apparatus in which means are provided to generate a magnetic field around the spark in order to additionally stabilize and constrict the same;

FIGURE 6 is a fragmentary cross-sectional view taken on line 6--6 of FIGURE 5; and

FIGURE 7 is an enlarged perspective view illustrating one of the electrodes of the embodiment of FIGURES 5 and 6, but with the insulation means not shown.

Referring first to FIGURES 1-3, inclusive, the apparatus is illustrated to comprise a pair of corresponding metal electrode elements 10 and 11 mounted in coaxial relationship and insulated from each other by a block 12 of insulating material. Stated more specifically, each electrode 10 and 11 has an enlarged, generally tubular base portion 13 provided with a radial flange 14 which abuts one end of insulating block 12, the latter being preferably a hollow cylinder or tube of transparent plastic such as Lucite. Integrally provided on the side of flange 14 opposite base 13 is a tubular plug portion 16 which fits closely into the cylindrical axial passage in insulating block 12. An arcing portion 17 is coaxially provided on the plug portion 16 and is generally tubular in shape, having a diameter smaller than that of the plug portion. The arcing portion terminates in a blunt radial end 18 which merges through a rounded edge 19 with the cylindrical side wall of the arcing portion.

From the above, it will be understood that the electrodes and the block 12 serve to define an annular cham- 3,313,980 Patented Apr. 11, 1967 ber 21 coaxially between the spaced radial ends 18 of the electrodes, the chamber having annulus portions 22 formed around the arcing portions 17 as best shown in FIGURES 2 and 3. In order to insure against leakage of gas from the chamber, O-rings 23 are provided between each flange 14 and the associated end of block 12 as illustrated in FIGURE 2.

A small-diameter cylindrical nozzle passage 24 is formed coaxially in each arcing portion 17 and communicates with a much larger passage 26, the latter extending coaxially through the electrode element 10 or 11 to the extreme outer end thereof. The nozzle passage 24 is relatively short, and the wall thereof may be suitably protected by a tubular insert, not shown, formed of tungsten or other refractory metal. Each large-diameter passage 26 may discharge to the atmosphere or may be connected to a conduit 27 leading to a suitable chamber, not shown, adapted to store the gas which is passed through the apparatus as will next be described.

Gas is introduced tangentially into chamber 21 through a passage 28 which is preferably located midway between the radial surfaces 18 and lies in a plane perpendicular to the axis of cylindrical chamber 21. The passage 28 communicates with a source 29 of gas, preferably an inert gas such as argon or helium, under substantial pressure.

The cross-sectional area of tangential passage 28 at its inlet opening 31 to chamber 21 is substantially smaller than the combined cross-sectional areas of both of the nozzle passages 24. For example, each of the passages 24 and the inlet opening 31 may have a diameter of .010 inch, so that the combined cross-sectional area of both discharge passages 24 is twice the cross-sectional area of inlet opening 31.

The inert gas from source 29 is introduced through inlet opening 31 at suificient pressure and velocity to whirl rapidly in the cylindrical chamber 21 and form a relatively clearly-defined vortex, indicated at 32 in FIGURE 1, coaxially between the two nozzle passages 24. The rapidly whirling or circulating gas then discharges through both passages 24- into the larger diameter passages 26, from whence it may either escape to the atmosphere or be recovered through conduits 27. The vortex has a very small diameter, for example less than the illustrated .010 inch diameter of each passage 24.

It is pointed out that the gas when it is introduced through inlet opening 31 has a pressure which is a number of times that in each passage 26, and that such pressure decreases radially toward the center of chamber 21 until the pressure at the center of the vortex 32 is substantially equal to that in the passage 26. The passage diameters and other factors are selected empirically to cause the pressure gradient adjacent vortex 32 to be relatively steep, thereby resulting in a well-defined low-resistance vortex surrounded by a rapidly circulating blanket or envelope of gas which acts as an insulating medium.

As an illustration, the gas pressure in chamber 21 at the peripheral portion thereof may be about p.s.i. absolute, whereas the pressure within the vortex 32 may be atmospheric. Furthermore, it is within the scope of the invention to connect the conduits 27 to a vacuum pump and thereby effect substantial evacuation of chamber 21, so that the inlet pressure adjacent opening 31 may be reduced substantially and still be many times that in passage 26.

Although the combined cross-sectional area of the discharge passages 24 should be greater than the cross-sectional area of inlet opening 31, it should not be so much greater that the gas pressure in chamber 21 radially outwardly of vortex 32 will be reduced .excessively. Instead, and as previously indicated, the pressure at the peripheral portion of chamber 21 should be a number of times the pressure in vortex 32.

A power source 33, adapted to deliver a very high-current pulse, is connected through a suitable trigger or switch apparatus 34 to both of the electrodes and 11. In the illustrated form, the leads 36 and 37 from the power source and trigger are connected to suitable conductor rings 38 provided around base portions 13 in electrically-conductive contact therewith. The power source 33 may comprise a low-inductance, high-capacity capacitor which is charged from a suitable direct current source, not shown. The trigger 34 may comprise an arc gap and a triggering electrode adapted to effect arcing across the gap when a voltage is applied to the electrode. The source 33 and the trigger 34 thus combine to effect flow of hundreds, thousands or millions of amperes of current through the electrodes 10 and 11 in a very short space of time such as a few milliseconds, microseconds or even a fraction of a microsecond.

It is pointed out that the cross-sectional area of chamber 21 is many times the cross-sectional area of each nozzle passage 24, and that the rapidly-circulating gas in chamber 21 effectively thermally insulates the electric spark or discharge from the cylindrical wall of the chamber 21.

Stated generally, the method comprises employing a rapidly-circulating fluid to constrict a high-intensity pulse discharge to a predetermined path of small cross-sectional area in order to achieve extremely high current densities and temperatures. More specifically, the method comprises passing fluid vortically between relatively blunt sparking electrodes and discharging the fluid through a nozzle passage in at least one of the electrodes to thereby confine the spark to the vortex and additionally to form plasma which passes through the nozzle passage.

With reference to the apparatus shown in FIGURES 1-3, the method comprises passing gas under relatively high pressure from source 23 through passage 28 and tangentially through inlet opening 31 into chamber 21. The gas whirls vortically and rapidly to define the indicated vortex 32 between the coaxial nozzle passages 24. The gas continuously discharges through both of the passages 24 into passages 26 which, as stated above, are at much lower pressure than the pressure in the peripheral portion of chamber 21.

While the gas is thus circulating in chamber 21, the trigger means 34 is employed to close the circuit through leads 36 and 37 from pulse source 33 to electrodes 10 and 11, thereby creating a highcurrent discharge between the arcing portions 17 of the electrodes. Because of the insulating characteristics of the blanket or envelope of gas around the vortex, the discharge is confined to the relatively low-resistance vortex 32 and therefore follows a straight path directly between the nozzle passages 24 instead of following the customary bent or circuitous path between the electrodes. Not only is the discharge caused to follow the straight path, it is constricted to the vortex 32 so that it has an extremely high current density with resulting high temperature. The extremely high temperature generated in vortex 32 converts the discharging gas into very high temperature plasma, so that streams of plasma are discharged through both of the nozzle passages 24 into passages 26.

It has been found that the discharge between arc portions 17 is more stable, and better confined to the vortex 32, where the electrodes are relatively blunt as distinguished from pointed. Thus, a previously indicated, the blunt ends 18 are employed instead of pointed or conical ends which are coaxial with the electrodes.

Except as will be specifically noted, the construction of FIGURE 4 is identical to that of FIGURES 1-3, and

corresponding reference numerals have been employed for corresponding parts.

The electrode 10 and associated apparatus is the same in FIGURE 4 as in FIGURES 1-3, and the electrode 11a is also identical except that the nozzle passage 24 and the connecting larger-diameter passage 26 are eliminated. The insulating block 12a is also the same, except that the tangential passage 28a and inlet opem'ng 31a are caused to be smaller than in the embodiment of FIG- URES 1-3 in order to compensate for the absence of the discharge passage in electrode 11a. Thus, inlet opening 31a has a diameter which is substantially smaller than that of the single nozzle passage 24.

The operation of the embodiment of FIGURE 4 is substantially the same as was previously described, except that the gas and plasma only discharge through the nozzle passage 24 in electrode 10, instead of discharging in opposite directions through both electrodes.

The construction shown in FIGURES 5-7 is the same as was described with relation to FIGURES 1-3, and has been correspondingly numbered, except that means are provided to effect a magnetic constricting and stabilizing action in addition to the above-described constriction by means of circulating fluid. This is accomplished by altering the construction of arcing portions 17b of electrodes 10b and 11b in such manner that the current pulse fOllOWs a loop-shaped path immediately prior to discharging through the vortex 32 (FIGURE 1).

Referring particularly to FIGURES 6 and 7, the arcing portion 17b of each electrode comprises a tubular metal cylinder 42 formed integral with an axially-extending olfset portion 43. A split ring or loop 44 is integrally connected at one of its ends to the forward end of offset portion 43, coaxial with the electrode and with chamber 21. The other end of ring 44 is connected through a radial connector 46 to a cylindrical terminal 47. Terminal 47 is also disposed coaxially of the electrode and of chamber 21 and is, similarly to the ring or loop 44, axially spaced from the end of the cylinder 42 by means of the olfset portion 43.

A complementary element 48, formed of insulating material, such as Teflon, is inserted in the ring 44 and associated elements in such manner that the resulting arcing portion 17 b is externally flush and cylindrical, having a radial face 18b formed cooperatively by elements 44, 47 and 48. It is pointed out that the radial connector 46 is set back from the surface 18b and is covered by insulation, so that the only conductor element adjacent the axis of chamber 21 is the forward end of the cylindrical terminal 47.

A cylindrical nozzle passage 49 i provided axially through the terminal 47 and the portion of insulator 48 inwardly thereof, such nozzle passage communicating with the previously-described larger diameter passage 26b.

The method with relation to the embodiment of FIG- URES 5-7 is the same as that of FIGURES 1-3, except with relation to the arcing portion 17b of each electrode 10b and 11b. Assuming that electrode 10b is positive and electrode 11b is negative, current flows from cylinder or tube portion 42 of electrode 10!) through offset portion 43, thence clockwise (as viewed in FIGURE 6) around the split ring 44 to radial connector 46, thence axially through cylinder 47 to'generate the discharge in the vortex in the whirling gas. The current thus reaches the portion 47 of the other electrode 11b and follows the reverse path to the opposite side of the pulse source.

It will thus be seen that the current at each end of the spark or discharge follows a loop-shaped path in a plane perpendicular to the discharge, and coaxially thereof. Lines of magnetic force are thus generated which bunch around the vortex in the whirling gas and constrict and stabilize the discharge between terminals 47. This action therefore cooperates with the constricting and stabilizing elfect of the whirling gas to provide a very stable discharge having an extremely elevated temperature. Such magnetic constricting and stabilizing action is highly effective because of the extremely large currents which are passed through the electrodes thereby generating strong magnetic fields for the purpose indicated.

Various embodiments of the present invention, in addition to what has been illustrated and described in detail,

may be employed without departing from the scope of the accompanying claim.

I claim:

A magnetically stabilized high pressure discharge lamp comprising an envelope containing an ionizable filling and having a pair of electrodes supported on inleads sealed therein, at least one of said electrodes having an emitting portion located on the lamp axis and surrounded by a coil providing circuit continuity from the inlead to the emitting portion, the turn of said coil generally surrounding said emitting portion but being spaced therefrom whereby current flowing to said emitting portion circulates through said coil and produces an axial magnetic field in said lamp, and means to eflect series flow through said coil, through said emitting portion and between said electrodes of a current which is sufficiently large that said axial magnetic field produces an efiective magnetic stabilization action on the electrical discharge which is generated in said envelope between said electrodes as the result of said current flow.

No references cited.

JAMES W. LAWRENCE, Primary Examiner.

ROBERT SEGAL, Examiner.

G. N. WESTBY, S. D. SCHLOSSER,

Assistant Examiners. 

